I have a login screen that I force to be ssl, so like this: https://www.foobar.com/login then after they login, they get moved to the homepage: https://www.foobar.com/dashba
I figured this out. Cake was switching the session.cookie_secure ini value on-the-fly while under SSL connections automatically, So the cookie being created was a secure cookie, which the second page wouldn't recognize.
Solution, comment out /cake/lib/session.php line 420 ish:
ini_set('session.cookie_secure', 1);
(Just search for that to find it, as I'm sure the line # will change as releases come out.)